Saehoon Ju

Investigation on the characteristics of the envelope FDTD based on the alternating direction implicit scheme

This letter presents numerical characteristics of recently developed the envelope FDTD based on the alternating direction implicit scheme (envelope ADI-FDTD). Through numerical simulations, it is shown that the envelope ADI-FDTD is unconditionally stable and we can get better dispersion accuracy than the traditional ADI-FDTD by analyzing the envelope of the signal. This fact gives the opportunity to extend the temporal step size to the Nyquist limit in certain cases. Numerical results show that the envelope ADI-FDTD can be used as an efficient electromagnetic analysis tool especially in the single frequency or band limited systems.

A study of the numerical dispersion relation for the 2-D ADI-FDTD method

This letter presents a numerical dispersion relation for the two-dimensional (2-D) finite-difference time-domain method based on the alternating-direction implicit time-marching scheme (2-D ADI-FDTD). The proposed analytical relation for 2-D ADI-FDTD is compared with those relations in the previous works. Through numerical tests, the dispersion equation of this work was shown as correct one for 2-D ADI-FDTD.

Application of the Modal CFS-PML-FDTD to the Analysis of Magnetic Photonic Crystal Waveguides

We develop a modal finite-difference time-domain (FDTD) method with a complex-frequency-shifted (CFS) perfectly matched layer (PML) to analyze magnetic photonic crystal (MPhC) waveguides. MPhCs are periodic structures with unit cell composed of two misaligned anisotropic dielectric layers and one ferromagnetic layer. Numerical results show that the proposed modal FDTD can reduce both memory and CPU costs by one order of magnitude or more compared to the conventional FDTD.

The modeling of thin-film bulk acoustic wave resonators using the FDTD method

The finite-difference time-domain (FDTD) technique has been applied to analyze electromechanical phenomena of thin-film bulk acoustic wave resonators (TFBARs) for the first time. To simulate several TFBARs that have one-dimensional (1-D) piezoelectric material variations, current-driven governing equations are discretized in spatial and temporal domain. The impedance characteristics are obtained by the proposed method and compared with the analytical solutions of the 1-D Mason model. Also, the values of lumped elements for the Butterworth Van Dyke (BVD) equivalent circuit are extracted. The results show that the proposed scheme has the potential to analyze the characteristics of arbitrary piezoelectric material embedded structures.

Investigation of an unconditionally stable compact 2D ADI-FDTD algorithm: formulations, numerical stability, and numerical dispersion

The alternating direction implicit finite-difference time-domain (ADIFDTD) scheme is applied to the compact two-dimensional FDTD (2D FDTD) for calculating dispersion characteristics of waveguide structures. The numerical stability and numerical dispersion of the compact 2D ADI-FDTD are also presented and investigated. Numerical wavelength for the dominant and higher order modes in hollow waveguide are obtained from the dispersion equation and compared with compact 2D FDTD results and analytic solutions.

Modal MRTD approaches for the efficient analysis of waveguide discontinuities

This paper, the multi-resolution time-domain (MRTD) technique is applied to the waveguide discontinuity problem for fast-scattering parameter computation. To improve the computational efficiency, both three-dimensional (3-D) waveguide regions, including discontinuities, and one dimensional (1-D) homogeneous waveguide region, terminated with the modal absorbing boundary condition (ABC), are simulated in the wavelet domain with the mode composition/expansion algorithm from the modal analysis. A WG-90 rectangular waveguide with a thick asymmetric iris is analyzed and the numerical results are compared with conventional finite-difference time-domain (FDTD) results and mode-matching results.

Parallel Dispersive FDTD Method Based on the Quadratic Complex Rational Function

Recently, the quadratic complex rational function (QCRF) function was proposed for accurate finite-difference time-domain (FDTD) dispersive modeling. First, this letter discusses two implementations of QCRF-FDTD to a zeroth-order temporal derivative term and it is observed that the numerical accuracy of the double averaging implementation is better than that of the direct implementation. Second, this work presents a fast QCRF-FDTD algorithm by employing a parallel processing algorithm. The proposed parallel QCRF-FDTD is validated in terms of the speedup fact and the computational accuracy. Finally, we analyze the shielding effectiveness of large-scale concrete structures by using our parallel QCRF-FDTD.

Study on Wideband Shielding Effects of Simple Building Structures Using FDTD Method

We perform a wideband radiated pulse coupling analysis of simple building structures using the finite-deference time-domain(FDTD) method. Toward this purpose, the building structures composed of concrete and window materials are assumed and we numerically model the electrical properties of each material. In this work, we apply a dispersive FDTD algorithm for the electromagnetic analysis of building structures and investigate their shielding effectiveness in the frequency range of 50 MHz to 1 GHz.

Impact of bandwidth on field enhancements effects in finite-size dispersion-engineered metamaterials

Photonic crystals (PhC) with a degenerate band edge (DBE) or a split band edge (SBE) yield dramatic field enhancement effects due to the interplay of slow-wave effects and Fabry-Perot resonances near the band-edge frequency. Numerical simulations are performed to investigate the impact of the fractional bandwidth (FBW) on field enhancement effects in both types of PhCs. The analysis is based on an unconditionally stable finite-difference time-domain (FDTD) method. We have found out that SBE PhCs can be less sensitive to the FBW than DBE PhCs when yielding similar performance.